diff --git a/vlib/builtin/js/array.js.v b/vlib/builtin/js/array.js.v
index 651e366b92..f98cfe8f25 100644
--- a/vlib/builtin/js/array.js.v
+++ b/vlib/builtin/js/array.js.v
@@ -138,7 +138,7 @@ pub fn (a array) str() string {
 #array.prototype[Symbol.iterator] = function () { return this.arr[Symbol.iterator](); }
 #array.prototype.entries = function () { return this.arr.entries(); }
 #array.prototype.map = function(callback) { return this.arr.map(callback); }
-#array.prototype.filter = function(callback) { return this.arr.filter(callback); }
+#array.prototype.filter = function(callback) { return new array(this.arr.filter( function (it) { return (+callback(it)) != 0; } )); }
 #Object.defineProperty(array.prototype,'cap',{ get: function () { return this.len; } })
 // delete deletes array element at index `i`.
 pub fn (mut a array) delete(i int) {
@@ -160,3 +160,23 @@ pub fn (mut a array) prepend(val voidptr) {
 pub fn (mut a array) prepend_many(val voidptr, size int) {
 	unsafe { a.insert_many(0, val, size) }
 }
+
+pub fn (a array) reverse() array {
+	mut res := array{}
+	#res.arr = Array.from(a.arr).reverse()
+
+	return res
+}
+
+#array.prototype.$includes = function (elem) { return this.arr.find(function(e) { return vEq(elem,e); }) !== undefined;}
+
+// reduce executes a given reducer function on each element of the array,
+// resulting in a single output value.
+pub fn (a array) reduce(iter fn (int, int) int, accum_start int) int {
+	mut accum_ := accum_start
+	#for (let i of a)  {
+	#accum_ = iter(accum_, a.arr[i])
+	#}
+
+	return accum_
+}
diff --git a/vlib/v/gen/js/builtin_types.v b/vlib/v/gen/js/builtin_types.v
index 6fb9115f0e..1bd1c15d47 100644
--- a/vlib/v/gen/js/builtin_types.v
+++ b/vlib/v/gen/js/builtin_types.v
@@ -263,6 +263,7 @@ struct BuiltinPrototypeConfig {
 	value_of      string = 'this.val'
 	to_string     string = 'this.val.toString()'
 	eq            string = 'this.val === other.val'
+	to_jsval      string = 'this'
 	extras        string
 	has_strfn     bool
 }
@@ -284,6 +285,7 @@ fn (mut g JsGen) gen_builtin_prototype(c BuiltinPrototypeConfig) {
 	g.writeln('valueOf() { return $c.value_of },')
 	g.writeln('toString() { return $c.to_string },')
 	g.writeln('eq(other) { return $c.eq },')
+	g.writeln('\$toJS() { return $c.to_jsval }, ')
 	if c.has_strfn {
 		g.writeln('str() { return new string(this.toString()) }')
 	}
@@ -306,6 +308,7 @@ fn (mut g JsGen) gen_builtin_type_defs() {
 					value_of: 'this.val | 0'
 					to_string: 'this.valueOf().toString()'
 					eq: 'this.valueOf() === other.valueOf()'
+					to_jsval: '+this'
 				)
 			}
 			'byte' {
@@ -316,18 +319,22 @@ fn (mut g JsGen) gen_builtin_type_defs() {
 					value_of: 'this.val | 0'
 					to_string: 'new string(this.val + "")'
 					eq: 'this.valueOf() === other.valueOf()'
+					to_jsval: '+this'
 				)
 			}
 			'f32', 'f64', 'float_literal' {
 				g.gen_builtin_prototype(
 					typ_name: typ_name
 					default_value: 'new Number(0)'
+					to_jsval: '+this'
 				)
 			}
 			'bool' {
 				g.gen_builtin_prototype(
+					constructor: 'this.val = +val !== 0'
 					typ_name: typ_name
 					default_value: 'new Boolean(false)'
+					to_jsval: '+this != 0'
 				)
 			}
 			'string' {
@@ -340,6 +347,7 @@ fn (mut g JsGen) gen_builtin_type_defs() {
 					to_string: 'this.str'
 					eq: 'this.str === other.str'
 					has_strfn: false
+					to_jsval: 'this.str'
 				)
 			}
 			'map' {
@@ -348,9 +356,10 @@ fn (mut g JsGen) gen_builtin_type_defs() {
 					val_name: 'map'
 					default_value: 'new Map()'
 					constructor: 'this.map = map'
-					value_of: 'this.map'
+					value_of: 'this'
 					to_string: 'this.map.toString()'
 					eq: 'vEq(this, other)'
+					to_jsval: 'this.map'
 				)
 			}
 			'array' {
@@ -359,9 +368,10 @@ fn (mut g JsGen) gen_builtin_type_defs() {
 					val_name: 'arr'
 					default_value: 'new Array()'
 					constructor: 'this.arr = arr'
-					value_of: 'this.arr'
+					value_of: 'this'
 					to_string: 'JSON.stringify(this.arr.map(it => it.valueOf()))'
 					eq: 'vEq(this, other)'
+					to_jsval: 'this.arr'
 				)
 			}
 			'any' {
@@ -373,6 +383,7 @@ fn (mut g JsGen) gen_builtin_type_defs() {
 					value_of: 'this.val'
 					to_string: '"&" + this.val'
 					eq: 'this == other' // compare by ptr
+					to_jsval: 'this.val.\$toJS()'
 				)
 			}
 			else {}
diff --git a/vlib/v/gen/js/fast_deep_equal.js b/vlib/v/gen/js/fast_deep_equal.js
index 9022d08444..0b0ae6a221 100644
--- a/vlib/v/gen/js/fast_deep_equal.js
+++ b/vlib/v/gen/js/fast_deep_equal.js
@@ -5,8 +5,8 @@ function vEq(a, b) {
 
 	if (a && b && typeof a == 'object' && typeof b == 'object') {
 		if (a.constructor !== b.constructor) return false;
-		a = a.valueOf();
-		b = b.valueOf();
+		a = a.$toJS();
+		b = b.$toJS();
 		var length, i, keys;
 		if (Array.isArray(a)) {
 			length = a.length;
diff --git a/vlib/v/gen/js/js.v b/vlib/v/gen/js/js.v
index 0119224e71..5bc985aff8 100644
--- a/vlib/v/gen/js/js.v
+++ b/vlib/v/gen/js/js.v
@@ -1079,6 +1079,7 @@ fn (mut g JsGen) gen_for_c_stmt(it ast.ForCStmt) {
 		g.write('; ')
 	}
 	if it.has_cond {
+		g.write('+') // convert to number or boolean
 		g.expr(it.cond)
 	}
 	g.write('; ')
@@ -1174,6 +1175,7 @@ fn (mut g JsGen) gen_for_stmt(it ast.ForStmt) {
 	if it.is_inf {
 		g.write('true')
 	} else {
+		g.write('+') // convert expr to number or boolean
 		g.expr(it.cond)
 	}
 	g.writeln(') {')
@@ -1325,6 +1327,7 @@ fn (mut g JsGen) gen_array_init_expr(it ast.ArrayInit) {
 	// offering similar performance
 	g.write('new array(')
 	g.inc_indent()
+
 	if it.has_len {
 		t1 := g.new_tmp_var()
 		t2 := g.new_tmp_var()
@@ -1349,6 +1352,31 @@ fn (mut g JsGen) gen_array_init_expr(it ast.ArrayInit) {
 		g.writeln('return $t1;')
 		g.dec_indent()
 		g.write('})()')
+	} else if it.is_fixed && it.exprs.len == 1 {
+		// [100]byte codegen
+		t1 := g.new_tmp_var()
+		t2 := g.new_tmp_var()
+		g.writeln('(function() {')
+		g.inc_indent()
+		g.writeln('const $t1 = [];')
+		g.write('for (let $t2 = 0; $t2 < ')
+		g.expr(it.exprs[0])
+		g.writeln('; $t2++) {')
+		g.inc_indent()
+		g.write('${t1}.push(')
+		if it.has_default {
+			g.expr(it.default_expr)
+		} else {
+			// Fill the array with the default values for its type
+			t := g.to_js_typ_val(it.elem_type)
+			g.write(t)
+		}
+		g.writeln(');')
+		g.dec_indent()
+		g.writeln('};')
+		g.writeln('return $t1;')
+		g.dec_indent()
+		g.write('})()')
 	} else {
 		g.gen_array_init_values(it.exprs)
 	}
@@ -1549,7 +1577,9 @@ fn (mut g JsGen) gen_if_expr(node ast.IfExpr) {
 				g.write(' : ')
 			}
 			if i < node.branches.len - 1 || !node.has_else {
+				g.write('(')
 				g.expr(branch.cond)
+				g.write(')')
 				g.write('.valueOf()')
 				g.write(' ? ')
 			}
@@ -1570,7 +1600,9 @@ fn (mut g JsGen) gen_if_expr(node ast.IfExpr) {
 						if '$branch.cond' == 'js' {
 							g.write('true')
 						} else {
+							g.write('(')
 							g.expr(branch.cond)
+							g.write(')')
 							g.write('.valueOf()')
 						}
 						g.writeln(') {')
@@ -1578,7 +1610,9 @@ fn (mut g JsGen) gen_if_expr(node ast.IfExpr) {
 				}
 			} else if i < node.branches.len - 1 || !node.has_else {
 				g.write('} else if (')
+				g.write('(')
 				g.expr(branch.cond)
+				g.write(')')
 				g.write('.valueOf()')
 				g.writeln(') {')
 			} else if i == node.branches.len - 1 && node.has_else {
@@ -1608,7 +1642,7 @@ fn (mut g JsGen) gen_index_expr(expr ast.IndexExpr) {
 	if expr.index is ast.RangeExpr {
 		g.expr(expr.left)
 		if expr.left_type.is_ptr() {
-			g.write('.val')
+			g.write('.valueOf()')
 		}
 		g.write('.slice(')
 		if expr.index.has_low {
@@ -1622,7 +1656,7 @@ fn (mut g JsGen) gen_index_expr(expr ast.IndexExpr) {
 		} else {
 			g.expr(expr.left)
 			if expr.left_type.is_ptr() {
-				g.write('.val')
+				g.write('.valueOf()')
 			}
 			g.write('.length')
 		}
@@ -1649,7 +1683,7 @@ fn (mut g JsGen) gen_index_expr(expr ast.IndexExpr) {
 			g.write('new byte(')
 			g.expr(expr.left)
 			if expr.left_type.is_ptr() {
-				g.write('.val')
+				g.write('.valueOf()')
 			}
 			g.write('.str.charCodeAt(')
 			g.expr(expr.index)
@@ -1659,10 +1693,10 @@ fn (mut g JsGen) gen_index_expr(expr ast.IndexExpr) {
 		// TODO Does this cover all cases?
 		g.expr(expr.left)
 		if expr.left_type.is_ptr() {
-			g.write('.val')
+			g.write('.valueOf()')
 		}
 		g.write('.arr')
-		g.write('[')
+		g.write('[+')
 		g.cast_stack << ast.int_type_idx
 		g.expr(expr.index)
 		g.cast_stack.delete_last()
@@ -1682,7 +1716,10 @@ fn (mut g JsGen) gen_infix_expr(it ast.InfixExpr) {
 	if it.op == .eq || it.op == .ne {
 		// Shallow equatables
 		if l_sym.kind in js.shallow_equatables && r_sym.kind in js.shallow_equatables {
+			// wrap left expr in parens so binary operations will work correctly.
+			g.write('(')
 			g.expr(it.left)
+			g.write(')')
 			g.write('.eq(')
 			g.cast_stack << int(l_sym.kind)
 			g.expr(it.right)
@@ -1713,7 +1750,7 @@ fn (mut g JsGen) gen_infix_expr(it ast.InfixExpr) {
 		} else if r_sym.kind == .string {
 			g.write('.str.includes(')
 		} else {
-			g.write('.arr.includes(')
+			g.write('.\$includes(')
 		}
 		g.expr(it.left)
 		if l_sym.kind == .string {
@@ -1728,14 +1765,15 @@ fn (mut g JsGen) gen_infix_expr(it ast.InfixExpr) {
 		is_arithmetic := it.op in [token.Kind.plus, .minus, .mul, .div, .mod]
 		mut needs_cast := is_arithmetic && it.left_type != it.right_type
 		mut greater_typ := 0
-		if needs_cast {
+		// todo(playX): looks like this cast is always required to perform .eq operation on types.
+		if true || needs_cast {
 			greater_typ = g.greater_typ(it.left_type, it.right_type)
 			if g.cast_stack.len > 0 {
 				needs_cast = g.cast_stack.last() != greater_typ
 			}
 		}
 
-		if needs_cast {
+		if true || needs_cast {
 			if g.ns.name == 'builtin' {
 				g.write('new ')
 			}
@@ -1746,7 +1784,7 @@ fn (mut g JsGen) gen_infix_expr(it ast.InfixExpr) {
 		g.write(' $it.op ')
 		g.expr(it.right)
 
-		if needs_cast {
+		if true || needs_cast {
 			g.cast_stack.delete_last()
 			g.write(')')
 		}
diff --git a/vlib/v/gen/js/temp_fast_deep_equal.v b/vlib/v/gen/js/temp_fast_deep_equal.v
index dac4f24cda..9015331a4c 100644
--- a/vlib/v/gen/js/temp_fast_deep_equal.v
+++ b/vlib/v/gen/js/temp_fast_deep_equal.v
@@ -9,8 +9,8 @@ function vEq(a, b) {
 
 	if (a && b && typeof a == 'object' && typeof b == 'object') {
 		if (a.constructor !== b.constructor) return false;
-		a = a.valueOf();
-		b = b.valueOf();
+		a = a.\$toJS();
+		b = b.\$toJS();
 		var length, i, keys;
 		if (Array.isArray(a)) {
 			length = a.length;
diff --git a/vlib/v/gen/js/tests/testdata/array.out b/vlib/v/gen/js/tests/testdata/array.out
index ffeaeacc6a..0822ce3c74 100644
--- a/vlib/v/gen/js/tests/testdata/array.out
+++ b/vlib/v/gen/js/tests/testdata/array.out
@@ -108,4 +108,57 @@ abc
 6
 1
 4
-6
\ No newline at end of file
+6
+[4,3,2,1]
+true
+true
+true
+true
+true
+true
+true
+0
+[0,0,0,0]
+[0,7,0,0]
+0
+[2,4,6,8,10,12,14,16,18,20]
+[2,4,6,8,10,12,14,16,18,20]
+[2,4,6,8,10]
+2
+[1,2]
+0
+1
+-1
+0
+3
+-1
+0
+2
+-1
+1
+2
+-1
+2
+3
+1
+3
+6
+true
+true
+true
+true
+true
+true
+true
+true
+true
+0
+0
+0
+0
+0
+[2,4,6]
+["is","awesome"]
+[2,3,4,6,8,9,10]
+[4,5,6]
+[5,10]
diff --git a/vlib/v/gen/js/tests/testdata/array.v b/vlib/v/gen/js/tests/testdata/array.v
index 3278bd46ce..53e9c1b409 100644
--- a/vlib/v/gen/js/tests/testdata/array.v
+++ b/vlib/v/gen/js/tests/testdata/array.v
@@ -6,6 +6,42 @@ struct Kkk {
 	q []Chunk
 }
 
+const (
+	c_n = 5
+)
+
+fn filter_test_helper_1(a int) bool {
+	return a > 3
+}
+
+fn sum(prev int, curr int) int {
+	return prev + curr
+}
+
+fn sub(prev int, curr int) int {
+	return prev - curr
+}
+
+struct Foooj {
+	a [5]int // c_n
+}
+
+fn double_up(mut a []int) {
+	for i := 0; i < a.len; i++ {
+		a[i] = a[i] * 2
+	}
+}
+
+fn double_up_v2(mut a []int) {
+	for i, _ in a {
+		a[i] = a[i] * 2 // or val*2, doesn't matter
+	}
+}
+
+fn modify(mut numbers []int) {
+	numbers[0] = 777
+}
+
 fn main() {
 	{
 		// test pointer
@@ -262,6 +298,7 @@ fn main() {
 		}
 	}
 	{
+		// todo(playX): deep repeat does not yet work.
 		/*
 		// test deep repeat
 		mut a3 := [[[1, 1], [2, 2], [3, 3]], [[4, 4], [5, 5], [6, 6]]]
@@ -319,4 +356,175 @@ fn main() {
 		println(a[3])
 		println(a[5])
 	}
+	{
+		// test reverse
+		a := [1, 2, 3, 4]
+		b := ['test', 'array', 'reverse']
+		c := a.reverse()
+		println(c)
+		d := b.reverse()
+		for i, _ in c {
+			println(c[i] == a[a.len - i - 1])
+		}
+		for i, _ in d {
+			println(d[i] == b[b.len - i - 1])
+		}
+		e := []int{}
+		f := e.reverse()
+		println(f.len)
+	}
+	{
+		// test fixed
+		mut nums := [4]int{}
+		// x := nums[1..3]
+		// assert x.len == 2
+
+		println(nums)
+		nums[1] = 7
+		println(nums)
+		nums2 := [5]int{} // c_n
+		println(nums2[c_n - 1])
+	}
+	{
+		// test mut slice
+		/*
+		todo(playX): slices do not work yet. We have to implement custom wrapper for them.
+		mut n := [1, 2, 3]
+		// modify(mut n)
+		modify(mut n[..2])
+		assert n[0] == 777
+		modify(mut n[2..])
+		assert n[2] == 777
+		println(n)
+		*/
+	}
+	{
+		// test mut arg
+		mut arr := [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+		double_up(mut arr)
+		println(arr.str())
+		arr = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+		double_up_v2(mut arr)
+		println(arr.str())
+	}
+	{
+		// test doubling
+		mut nums := [1, 2, 3, 4, 5]
+		for i in 0 .. nums.len {
+			nums[i] *= 2
+		}
+		println(nums.str())
+	}
+	{
+		// test single element
+
+		mut a := [1]
+		a << 2
+		println(a.len)
+		assert a[0] == 1
+		assert a[1] == 2
+		println(a)
+	}
+	{
+		// test find index
+
+		// string
+		a := ['v', 'is', 'great']
+		println(a.index('v'))
+		println(a.index('is'))
+		println(a.index('gre'))
+		// int
+		b := [1, 2, 3, 4]
+		println(b.index(1))
+		println(b.index(4))
+		println(b.index(5))
+		// byte
+		c := [0x22, 0x33, 0x55]
+		println(c.index(0x22))
+		println(c.index(0x55))
+		println(c.index(0x99))
+		// char
+		d := [`a`, `b`, `c`]
+		println(d.index(`b`))
+		println(d.index(`c`))
+		println(d.index(`u`))
+	}
+	{
+		// test multi
+
+		a := [[1, 2, 3], [4, 5, 6]]
+		println(a.len)
+		println(a[0].len)
+		println(a[0][0])
+		println(a[0][2])
+		println(a[1][2])
+	}
+	{
+		// test in
+		a := [1, 2, 3]
+		println(1 in a)
+		println(2 in a)
+		println(3 in a)
+		println(!(4 in a))
+		println(!(0 in a))
+		println(0 !in a)
+		println(4 !in a)
+		b := [1, 4, 0]
+		c := [3, 6, 2, 0]
+		println(0 in b)
+		println(0 in c)
+	}
+	{
+		// test reduce
+		a := [1, 2, 3, 4, 5]
+		b := a.reduce(sum, 0)
+		c := a.reduce(sum, 5)
+		d := a.reduce(sum, -1)
+		println(b)
+		println(c)
+		println(d)
+		e := [1, 2, 3]
+		f := e.reduce(sub, 0)
+		g := e.reduce(sub, -1)
+		println(f)
+		println(g)
+	}
+	{
+		a := [1, 2, 3, 4, 5, 6]
+		b := a.filter(it % 2 == 0)
+		println(b)
+
+		c := ['v', 'is', 'awesome']
+		d := c.filter(it.len > 1)
+		println(d)
+		assert d[0] == 'is'
+		assert d[1] == 'awesome'
+		////////
+		arr := [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+		println(arr.filter(it % 2 == 0 || it % 3 == 0))
+
+		mut mut_arr := [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
+		mut_arr = mut_arr.filter(it < 4)
+		assert mut_arr.len == 3
+		println(a.filter(filter_test_helper_1))
+		println([1, 5, 10].filter(filter_test_helper_1))
+	}
+	{
+		// todo(playX): RUNTIME ERROR: Invalid memory access
+		/*
+		// test anon fn filter
+		filter_num := fn (i int) bool {
+			return i % 2 == 0
+		}
+		assert [1, 2, 3, 4, 5].filter(filter_num) == [2, 4]
+		*/
+	}
+	{
+		/*
+		a := [1, 2, 3, 4].filter(fn (i int) bool {
+			return i % 2 == 0
+		})
+		assert a == [2, 4]
+		*/
+	}
 }